"At the Olympics, Brody won his solo events, but messed up the team relay because he got drunk the night before," Efron says. "He did some illegal stuff, and joining Baywatch is part of his parole.

"For Mitch, joining Baywatch is a highly competitive honour that has to be earned. But for Brody, it's a punishment."

Zac Efron attends the Australian premiere of Baywatch in Sydney, Australia. Supplied by Paramount Pictures.Brendon Thorne

Despite their differences, and Brody's tendency to jump head-first into rescue situations without thinking things through, Mitch and Brody must work together with the rest of the team to uncover a local criminal plot that threatens the future of the Bay.

This new Baywatch is a buddy comedy of sorts full of "filthy fun'', as Johnson describes it.

"He's always willing to push the envelope... the more insults and jabs he gave to my character, I was secretly taking as compliments because it was just kind of cool," Efron says.

While he's known for his physical fitness and "10-pack'' abs, Efron had to work hard to bulk up and then maintain the body of an Olympic swimmer. "I built a gym in my garage... it was rough but it worked," he says.

"Every morning between 4.30am and 5am I'd do a training session and then it was hair and make-up (laughs). You're like pumping iron and then you're getting your make-up done. It was literally manliness and then manliness reversed."

Growing up a few hours north of Los Angeles, Efron wasn't allowed to watch the original Baywatch TV series.

"I wasn't allowed to watch Baywatch," he says. "But I do remember sneaking it, late at night, after Howard Stern on a crappy old TV with a dial. One time, I was channel flipping and came across this awesome show full of boats and explosions and I just thought the whole thing was amazing."

Efron's a keen surfer but admits his ocean skills would never stack up to the likes of a professional lifeguard.

"Ocean swims and rip tides, all that stuff is incredibly difficult," he says. "I want to master it so bad, but it's really difficult and I'm still working on it.

"Even with this movie with the coaches, the ocean swims were always the scariest."

Baywatch also stars Alexandra Daddario and Jon Bass as bright young recruits Summer Quinn and Ronnie Greenbaum, Ilfenesh Hadera as Mitch's second-in-command Stephanie Holden, and Sports Illustrated swimsuit model Kelly Rohrbach as CJ Parker - the role made famous by Pamela Anderson.